Large field-of-view quantitative phase imaging flow cytometry using low coherence SLD based digital holographic microscopy

We present a cost-effective quantitative phase imaging flow cytometry system that utilizes a low-coherence super luminescent diode (SLD) as the illumination source for off-axis digital holographic microscopy (DHM), enabling label-free imaging of biological cells in flow. While off-axis DHM systems for flow imaging typically rely on expensive coherent lasers, our system employs a low-coherence SLD to reduce both cost and coherence noise. Achieving a large field of view with low-coherence sources is inherently challenging due to limited coherence length; in this work, we address this by incorporating a diffraction grating in the reference beam, which enables large-area interference and supports parallel imaging of multiple cells for high-throughput analysis. The system maintains a short exposure time of 50 μs—critical for dynamic single-cell studies—while achieving a signal-to-noise ratio (SNR) of 48, enabled by the high optical power and low coherence of the SLD, which together reduce coherence noise and enhance SNR. Jurkat cells in flow were imaged using this integrated setup, and system characterization confirmed high spatial phase sensitivity and stable temporal stability. The integrated microfluidic flow control system, featuring a three-way valve, enabled sedimentation-free flow at lower flow rates. Quantitative morphological analysis confirmed that native cell shape was preserved during flow, demonstrating the system’s suitability for label-free imaging of single-cell morphology. This platform provides a scalable, high-performance solution for real-time cellular analysis and non-invasive imaging, with translational potential in biomedical and diagnostic applications.